This action research study examines the use of professional development to build the self-efficacy of secondary math teachers in culturally responsive mathematics teaching (CRMT), with the hope to address achievement gaps of Black and Hispanic students. Seven math teachers from a school division in Southwest Virginia participated in a 9-week professional development that included virtual meetings to learn about CRMT, collaboration with colleagues, classroom applications, and self-reflection. Quantitative and qualitative data were collected throughout the 9 weeks in the forms of questionnaires, meeting transcripts, and reflection journals. The research study results found the professional development to build teacher self-efficacy, especially with the key aspects of collaboration, classroom application, and reflection. Further research may be helpful to learn how to best train teachers on how to find and use CRMT resources with the demands of state and national curriculum standards, testing, and school division initiatives. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]